The current climate change is more rapid contrasted to the previous period of changes, probably caused by the emission of greenhouse gases (CO2 and Methane). Greenhouse gases allow heat to reach the earth's surface as it is transparent to sunlight. It amplifies by the loss of sun-reflecting snow cover as the planet heats.
Since the industrial revolution, there have been changes in the average surface air temperature due to human activity and natural forces adding variability. The temperature has risen twice as fast as the global average on land. There have also been environmental changes in coral reefs, mountains, dessert, etc. Human migration and conflict might result in climatic changes threatening people with food and water scarcity, economic loss, increased flood, extreme heat, etc. According to the World Health Organization, climate change is the greatest danger to global health in the 21st CE.
Terminologies/Jargons: The terms global warming and climatic change became popular in the 1980s. Global warming usually refers to human invoked warming, whereas climate change refers to natural changes. To refer to human impact on the climate, scientist often uses the term incidental or inadvertent climate modification. Instead of global warming, the terms climate crisis or climate emergency is used to talk about the climatic changes. In 2019, oxford chose 'climate emergency' as the word of the year, being included in the editorial guidelines to become scientifically precise while communicating clearly with the readers on important issues.
Observed Temperature: Statistics show that the number of warm days and nights has increased about 0.2°C per decade compared to the pre-industrial baseline (2011-2020 decade). Around 1850, Thermometer records provided global coverage of temperature. The information of this period comes from climate proxies such as trees, ice cores, etc. There have been numerous issues of global warming like the Paleocene-Eocene Thermal Maximum. As the observed rise in temperature and CO2 concentrations have been rapid, sudden geographical events in the earth's history do not approach it. Shreds of evidence of warming from other observations as air temperature measurements were substantiated. The high frequency and intensity of rain, melting of snow, and land ice led to the increment of atmospheric humidity. As oceans lose heat by the process of evaporation, the average surface temperature since the pre-industrial period has increased almost twice as fast as the global average temperature. The northern hemisphere has more seasonal snow cover and sea ice along with the lands. The deposition of carbon on snow and ice leads to disruption. After the ice melts, they start absorbing heat from reflecting a lot of light to being dark as the surface flips.
Rising temperature causes: Some factors like greenhouse gases, volcanic eruptions, variation around the sun, etc. cause an energy imbalance (external) to the climate system.
- Greenhouse- Since the year 1750(industrial revolution), the concentrations of CO2 and methane increased about 48% and 160%, respectively. Human interference, like the extraction and burning of fossil fuels such as coal, natural gas, etc. raises the number of greenhouse gases in the atmosphere to cause a radiative imbalance.
- Aerosol- Aerosols (smoke, fog, and mist) scatter and absorb radiation causing indirect effects on the same.
- Volcanic Activity- Volcanic eruptions represent natural forcing over the industrial era, but they didn't have that much of an impact globally. Solar radiation is measured directly by satellites, while indirect measurements started from the 1600s onwards.
- Modifications and Feedback- Feedback modifies the response of the climatic system. It can either be raised by self-reinforcement or balancing feedback. One of the main reasons for the projection of different magnitudes for a given amount of emission is due to uncertainty over feedback. Another important reason is the reduction of snow cover and sea ice in the Arctic reducing the reflectivity of the earth's surface.
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